Does Phase support creating new sound events at runtime? Is that implemented in the plugin for Unity as well? Does Phase support Unity's addressable system, are they compatible?
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Hi, In my project I am using AVFoundation for recording the audio. We are using AVAudioMixerNode class below method to record the audio packet.
**func installTap(
onBus bus: AVAudioNodeBus,
bufferSize: AVAudioFrameCount,
format: AVAudioFormat?,
block tapBlock: @escaping AVAudioNodeTapBlock
)
**
It works perfectly fine.
But in production env some small percentage of the user we are facing issue like after recording few packets it stops automatically without stopping the audio engine. Can anyone help here that why this happens? I have also observed for mediaServicesWereResetNotification and added log on receiving this notification but when this issue happens I don't see any occurence of this log. Also is there any callback when the engine stops?
On Apple TV 4K 3rd generation, with tvOS 26 beta 2, when two HomePod 2 are paired to the device, music and movie sources with Dolby Atmos can only be listened to in stereo. dolby atmos not supported
Topic:
Media Technologies
SubTopic:
Audio
Is there a way to destroy MIDIUMPMutableEndpoint again?
In my app, the user has a setting to enable and disable MIDI 2.0. If MIDI 2.0 should not be supported (or if iOS version < 18), it creates a virtual destination and a virtual source. And if MIDI 2.0 should be enabled, it instead creates a MIDIUMPMutableEndpoint, which itself creates the virtual destination and source automatically.
So here is my problem: I didn't find any way to destroy the MIDIUMPMutableEndpoint again. There is a method to disable it (setEnabled:NO), but that doesn't destroy or hide the virtual destination and source. So when the user turns MIDI 2.0 support off, I will have two virtual destinations and sources, and cannot get rid of the 2.0 ones.
What is the correct way to get rid of the MIDIUMPMutableEndpoint once it is created?
Hello,
I'm trying to determine the best/recommended AVAudioSession configuration (i.e category, mode, and options) for the following use-case.
Essentially, I'd like to switch between periods of playing an audio file and then recognizing speech. The audio file is typically speech and I don't intend for playback and speech recognition to occur simultaneously. I'd like for the user to sill be able to interact with Siri and I'd like for it to work with CarPlay where navigation prompts can occur.
I would assume the category to use is 'playAndRecord', but I'm not sure if it's better to just set that once for the entire lifecycle, or set to 'playback' for audio file playback and then switch to 'playAndRecord' for speech recognition . I'm also not sure on the best 'mode' and 'options' to set. Any suggestions would be appreciated.
Thanks.
We’ve encountered a reproducible issue where the iPhone fails to reconnect to a Wi-Fi access point under the following conditions:
The device is connected to a 2.4GHz Wi-Fi network.
A Bluetooth audio accessory is connected (e.g. headset).
AVAudioSession is active (such as during a voice call or when using the Voice Memos app).
The user moves away from the access point, causing a disconnect.
Upon returning within range, the access point is no longer recognized or reconnected while AVAudioSession remains active.
However, if the Bluetooth device is disconnected or the AVAudioSession is deactivated, the Wi-Fi access point is immediately recognized again.
We confirmed this behavior not only in my app but also using Apple's built-in Voice Memos app, suggesting this is not specific to our implementation.
It appears that the Wi-Fi system deprioritizes reconnection while AVAudioSession is engaged. Could this be by design? Or is this a known issue or limitation with Wi-Fi and AVAudioSession interaction?
Test Environment:
Device: iPhone 13 mini
iOS: 17.5.1
Wi-Fi: 2.4GHz band
Accessories: Bluetooth headset
We’d appreciate clarification on whether this is expected behavior or a bug. Thank you!
I've been trying to use AVMIDIControlChangeEvent with a bankSelect message type to change the instrument the sequencer uses on a AVMusicTrack with no luck.
I started with the Apple AVAEMixerSample, converting the initial setup/loading and portions dealing with the sequencer to Swift. I got that working and playing the "bluesyRiff" and then modified it to play individual notes. So my createAndSetupSequencer looked like
func createAndSetupSequencer() {
sequencer = AVAudioSequencer(audioEngine: engine)
// guard let midiFileURL = Bundle.main.url(forResource: "bluesyRiff", withExtension: "mid") else {
// print (" failed guard trying to get URL for bluesyRiff")
// return
// }
let track = sequencer.createAndAppendTrack()
var currTime = 1.0
for i: UInt32 in 0...8 {
let newNoteEvent = AVMIDINoteEvent(channel: 0, key: 60+i, velocity: 64, duration: 2.0)
track.addEvent(newNoteEvent, at: AVMusicTimeStamp(currTime))
currTime += 2.0
}
The notes played, so then I also replaced the gs_instruments sound bank with GeneralUser GS MuseScore v1.442 first by trying
guard let soundBankURL = Bundle.main.url(forResource: "GeneralUser GS MuseScore v1.442", withExtension: "sf2") else {
return}
do {
try sampler.loadSoundBankInstrument(at: soundBankURL, program: 0x001C, bankMSB: 0x79, bankLSB: 0x08)
} catch{....
}
This appears to work, the instrument (8 which is "Funk Guitar") plays. If I change to bankLSB: 0x00 I get the "Palm Muted guitar". So I know that the soundfont has these instruments
Stuff goes off the rails when I try to change the instruments in createAndSetupSequencer. Putting
let programChange = AVMIDIProgramChangeEvent(channel: 0, programNumber: 0x001C)
let bankChange = AVMIDIControlChangeEvent(channel: 0, messageType: AVMIDIControlChangeEvent.MessageType.bankSelect, value: 0x00)
track.addEvent(programChange, at: AVMusicTimeStamp(1.0))
track.addEvent(bankChange, at: AVMusicTimeStamp(1.0))
just before my add note loop doesn't produce any change. Loading bankLSB 8 (Funk) in sampler.loadSoundBankInstrument and trying to change with bankSelect 0 (Palm muted) in createAndSetupSequencer results in instrument 8 (Funk) playing not Palm Muted.
Loading bankLSB 0 (Palm muted) and trying to change with bankSelect 8 (Funk) doesn't work, 0 (Palm muted) plays
I also tried sampler.loadInstrument(at: soundBankURL) and then I always get the first instrument in the sound font file (piano)no matter what values I put in my programChange/bankChange
I've also changed the time in the track.addEvent to be 0, 1.0, 3.0 etc to no success
The sampler.loadSoundBankInstrument specifies two UInt8 parameters, bankMSB and BankLSB while the AVMIDIControlChangeEvent bankSelect value is UInt32 suggesting it might be some combination of bankMSB and BankLSB. But the documentation makes no mention of what this should look like. I tried various combinations of 0x7908, 0X0879 etc to no avail
I will also point out that I am able to successfully execute other control change events
For example adding
if i == 1 {
let portamentoOnEvent = AVMIDIControlChangeEvent(channel: 0, messageType: AVMIDIControlChangeEvent.MessageType.portamento, value: 0xFF)
track.addEvent(portamentoOnEvent, at: AVMusicTimeStamp(currTime))
let portamentoRateEvent = AVMIDIControlChangeEvent(channel: 0, messageType: AVMIDIControlChangeEvent.MessageType.portamentoTime, value: 64)
track.addEvent(portamentoRateEvent, at: AVMusicTimeStamp(currTime))
}
does produce a change in the sound. (As an aside, a definition of what portamento time is, other than "the rate of portamento" would be welcome. is it notes/seconds? freq/minute? beats/hour?)
I was able to get the instrument to change in a different program using MusicPlayer and a series of MusicTrackNewMIDIChannelEvent on a track but these operate on a MusicTrack not the AVMusicTrack which the sequencer uses.
Has anyone been successful in switching instruments through an AVMIDIControlChangeEvent or have any feedback on how to do this?
Hi,
I'm still stuck getting a basic record-with-playthrouh pipeline to work.
Has anyone a sample of setting up a AVAudioEngine pipeline for recording with playthrough?
Plkaythrough works with AVPlayerNode as input but not with any microphone input. The docs mention the "enabled state" of the outputNode of the engine without explaining the concept, i.e. how to enable an output.
When the engine renders to and from an audio device, the AVAudioSession category and the availability of hardware determines whether an app performs output. Check the output node’s output format (specifically, the hardware format) for a nonzero sample rate and channel count to see if output is in an enabled state.
Well, in my setup the output is NOT enabled, and any attempt to switch (e.g. audioEngine.outputNode.auAudioUnit.setDeviceID(deviceID) )/ attach a dedicated device / ... results in exceptions / errors
I’m running HomePod OS 26 on two HomePod minis and OS 18.6 on main HomePod (original)
I’ve enabled Crossfade in the Home app.
I’m playing Apple Music directly in the HomePod mini.
Crossfade just doesn’t work on any HomePod.
I can understand it not working on the HomePod - but why isn’t it working on the minis running OS 26?
I’ve tried disabling and enabling Crossfade, rebooting HomePods etc but nothing?!
I’m an amateur developer working on a free utility for composers/producers, for which the macOS release needs to create and name RTP-MIDI sessions in Audio MIDI Setup from the command line (so I can ship a small C helper instead of telling users to click through the UI). Here’s what I’ve tried so far, without luck:
• Plist hacks: Injecting entries into ~/Library/Audio/MIDI Configurations/*.mcfg works when AMS is closed, but AMS immediately locks and reverts my changes when it’s open.
• CoreMIDI C API: I can create virtual ports with MIDISourceCreate, but attempting MIDIObjectGetDataProperty on the apple.midirtp.session plugin always returns err –10836.
• Obj-C & Swift: Loading MIDINetworkSession and calling defaultSession, init, setNetworkName: and setting enabled = YES doesn’t produce a new session object in the Network panel.
• dlopen/dlsym: I extracted the real CoreMIDI binary out of the dyld shared cache and tried binding _MIDINetworkSessionCreate, _SetName, _SetEnabled, etc., but all the symbols come back null or my tool segfaults.
• Plugin registration: I’ve pulled the factory UUID (70C9C5EA-7C65-11D8-B317-000393A34B5A) from /System/Library/Extensions/AppleMIDIRTPDriver.plugin/Contents/Info.plist and called CFPlugInRegisterFactories, but it still never exposes the session-creation calls.
At this point I’m convinced I’m either loading the wrong binary or missing one critical step in registering the RTP-MIDI plugin’s private API. Can anyone point me to:
The exact path of the dylib or bundle that actually exports the MIDINetworkSessionCreate/MIDINetworkSessionSetName/MIDINetworkSessionSetEnabled symbols?
A minimal working snippet (C or Obj-C) that reliably creates and names a Network-MIDI session?
Any pointers, sample code, or even ideas about where Apple hides this functionality on macOS 15 would be hugely appreciated. Thanks!
I am trying to get MIDI output from the AU Host demo app using the recent MIDI processor example. The processor works correctly in Logic Pro, but I cannot send MIDI from the AUv3 extension in standalone mode using the default host app to another program (e.g., Ableton).
The MIDI manager, which is part of the standalone host app, works fine, and I can send MIDI using it directly—Ableton receives it without issues. I have already set the midiOutputNames in the extension, and the midiOutBlock is mapped. However, the MIDI data from the AUv3 extension does not reach Ableton in standalone mode. I suspect the issue is that midiOutBlock might never be called in the plugin, or perhaps an input to the plugin is missing, which prevents it from sending MIDI. I am currently using the default routing.
I have modified the MIDI manager such that it works well as described above. Here is a part of my code for SimplePlayEngine.swift and my MIDIManager.swift for reference:
@MainActor
@Observable
public class SimplePlayEngine {
private let midiOutBlock: AUMIDIOutputEventBlock = { sampleTime, cable, length, data in return noErr }
var scheduleMIDIEventListBlock: AUMIDIEventListBlock? = nil
public init() {
engine.attach(player)
engine.prepare()
setupMIDI()
}
private func setupMIDI() {
if !MIDIManager.shared.setupPort(midiProtocol: MIDIProtocolID._2_0, receiveBlock: { [weak self] eventList, _ in
if let scheduleMIDIEventListBlock = self?.scheduleMIDIEventListBlock {
_ = scheduleMIDIEventListBlock(AUEventSampleTimeImmediate, 0, eventList)
}
}) {
fatalError("Failed to setup Core MIDI")
}
}
func initComponent(type: String, subType: String, manufacturer: String) async -> ViewController? {
reset()
guard let component = AVAudioUnit.findComponent(type: type, subType: subType, manufacturer: manufacturer) else {
fatalError("Failed to find component with type: \(type), subtype: \(subType), manufacturer: \(manufacturer))" )
}
do {
let audioUnit = try await AVAudioUnit.instantiate(
with: component.audioComponentDescription, options: AudioComponentInstantiationOptions.loadOutOfProcess)
self.avAudioUnit = audioUnit
self.connect(avAudioUnit: audioUnit)
return await audioUnit.loadAudioUnitViewController()
} catch {
return nil
}
}
private func startPlayingInternal() {
guard let avAudioUnit = self.avAudioUnit else { return }
setSessionActive(true)
if avAudioUnit.wantsAudioInput { scheduleEffectLoop() }
let hardwareFormat = engine.outputNode.outputFormat(forBus: 0)
engine.connect(engine.mainMixerNode, to: engine.outputNode, format: hardwareFormat)
do { try engine.start() } catch {
isPlaying = false
fatalError("Could not start engine. error: \(error).")
}
if avAudioUnit.wantsAudioInput { player.play() }
isPlaying = true
}
private func resetAudioLoop() {
guard let avAudioUnit = self.avAudioUnit else { return }
if avAudioUnit.wantsAudioInput {
guard let format = file?.processingFormat else { fatalError("No AVAudioFile defined.") }
engine.connect(player, to: engine.mainMixerNode, format: format)
}
}
public func connect(avAudioUnit: AVAudioUnit?, completion: @escaping (() -> Void) = {}) {
guard let avAudioUnit = self.avAudioUnit else { return }
engine.disconnectNodeInput(engine.mainMixerNode)
resetAudioLoop()
engine.detach(avAudioUnit)
func rewiringComplete() {
scheduleMIDIEventListBlock = auAudioUnit.scheduleMIDIEventListBlock
if isPlaying { player.play() }
completion()
}
let hardwareFormat = engine.outputNode.outputFormat(forBus: 0)
engine.connect(engine.mainMixerNode, to: engine.outputNode, format: hardwareFormat)
if isPlaying { player.pause() }
let auAudioUnit = avAudioUnit.auAudioUnit
if !auAudioUnit.midiOutputNames.isEmpty { auAudioUnit.midiOutputEventBlock = midiOutBlock }
engine.attach(avAudioUnit)
if avAudioUnit.wantsAudioInput {
engine.disconnectNodeInput(engine.mainMixerNode)
if let format = file?.processingFormat {
engine.connect(player, to: avAudioUnit, format: format)
engine.connect(avAudioUnit, to: engine.mainMixerNode, format: format)
}
} else {
let stereoFormat = AVAudioFormat(standardFormatWithSampleRate: hardwareFormat.sampleRate, channels: 2)
engine.connect(avAudioUnit, to: engine.mainMixerNode, format: stereoFormat)
}
rewiringComplete()
}
}
and my MIDI Manager
@MainActor
class MIDIManager: Identifiable, ObservableObject {
func setupPort(midiProtocol: MIDIProtocolID,
receiveBlock: @escaping @Sendable MIDIReceiveBlock) -> Bool {
guard setupClient() else { return false }
if MIDIInputPortCreateWithProtocol(client, portName, midiProtocol, &port, receiveBlock) != noErr {
return false
}
for source in self.sources {
if MIDIPortConnectSource(port, source, nil) != noErr {
print("Failed to connect to source \(source)")
return false
}
}
setupVirtualMIDIOutput()
return true
}
private func setupVirtualMIDIOutput() {
let virtualStatus = MIDISourceCreate(client, virtualSourceName, &virtualSource)
if virtualStatus != noErr {
print("❌ Failed to create virtual MIDI source: \(virtualStatus)")
} else {
print("✅ Created virtual MIDI source: \(virtualSourceName)")
}
}
func sendMIDIData(_ data: [UInt8]) {
print("hey")
var packetList = MIDIPacketList()
withUnsafeMutablePointer(to: &packetList) { ptr in
let pkt = MIDIPacketListInit(ptr)
_ = MIDIPacketListAdd(ptr, 1024, pkt, 0, data.count, data)
if virtualSource != 0 {
let status = MIDIReceived(virtualSource, ptr)
if status != noErr {
print("❌ Failed to send MIDI data: \(status)")
} else {
print("✅ Sent MIDI data: \(data)")
}
}
}
}
}
A bit of a novice to app development here but I have a paid developer account, I have registered the identifier for MusicKit on the developer website (using the bundle identifier I've selected in Xcode) but the option to add MusicKit as a capability is not available in Xcode?
I've manually updated the certificates, closed the app and reopened it, started a new project and tried with a different demo project?
Apologies if I am missing something obvious but could someone help me get this capability added?
I'm streaming mp3 audio data using URLSession/AudioFileStream/AVAudioConverter and getting occasional silent buffers and glitches (little bleeps and whoops as opposed to clicks). The issues are present in an offline test, so this isn't an issue of underruns.
Doing some buffering on the input coming from the URLSession (URLSessionDataTask) reduces the glitches/silent buffers to rather infrequent, but they do still happen occasionally.
var bufferedData = Data()
func parseBytes(data: Data) {
bufferedData.append(data)
// XXX: this buffering reduces glitching
// to rather infrequent. But why?
if bufferedData.count > 32768 {
bufferedData.withUnsafeBytes { (bytes: UnsafeRawBufferPointer) in
guard let baseAddress = bytes.baseAddress else { return }
let result = AudioFileStreamParseBytes(audioStream!,
UInt32(bufferedData.count),
baseAddress,
[])
if result != noErr {
print("❌ error parsing stream: \(result)")
}
}
bufferedData = Data()
}
}
No errors are returned by AudioFileStream or AVAudioConverter.
func handlePackets(data: Data,
packetDescriptions: [AudioStreamPacketDescription]) {
guard let audioConverter else {
return
}
var maxPacketSize: UInt32 = 0
for packetDescription in packetDescriptions {
maxPacketSize = max(maxPacketSize, packetDescription.mDataByteSize)
if packetDescription.mDataByteSize == 0 {
print("EMPTY PACKET")
}
if Int(packetDescription.mStartOffset) + Int(packetDescription.mDataByteSize) > data.count {
print("❌ Invalid packet: offset \(packetDescription.mStartOffset) + size \(packetDescription.mDataByteSize) > data.count \(data.count)")
}
}
let bufferIn = AVAudioCompressedBuffer(format: inFormat!, packetCapacity: AVAudioPacketCount(packetDescriptions.count), maximumPacketSize: Int(maxPacketSize))
bufferIn.byteLength = UInt32(data.count)
for i in 0 ..< Int(packetDescriptions.count) {
bufferIn.packetDescriptions![i] = packetDescriptions[i]
}
bufferIn.packetCount = AVAudioPacketCount(packetDescriptions.count)
_ = data.withUnsafeBytes { ptr in
memcpy(bufferIn.data, ptr.baseAddress, data.count)
}
if verbose {
print("handlePackets: \(data.count) bytes")
}
// Setup input provider closure
var inputProvided = false
let inputBlock: AVAudioConverterInputBlock = { packetCount, statusPtr in
if !inputProvided {
inputProvided = true
statusPtr.pointee = .haveData
return bufferIn
} else {
statusPtr.pointee = .noDataNow
return nil
}
}
// Loop until converter runs dry or is done
while true {
let bufferOut = AVAudioPCMBuffer(pcmFormat: outFormat, frameCapacity: 4096)!
bufferOut.frameLength = 0
var error: NSError?
let status = audioConverter.convert(to: bufferOut, error: &error, withInputFrom: inputBlock)
switch status {
case .haveData:
if verbose {
print("✅ convert returned haveData: \(bufferOut.frameLength) frames")
}
if bufferOut.frameLength > 0 {
if bufferOut.isSilent {
print("(haveData) SILENT BUFFER at frame \(totalFrames), pending: \(pendingFrames), inputPackets=\(bufferIn.packetCount), outputFrames=\(bufferOut.frameLength)")
}
outBuffers.append(bufferOut)
totalFrames += Int(bufferOut.frameLength)
}
case .inputRanDry:
if verbose {
print("🔁 convert returned inputRanDry: \(bufferOut.frameLength) frames")
}
if bufferOut.frameLength > 0 {
if bufferOut.isSilent {
print("(inputRanDry) SILENT BUFFER at frame \(totalFrames), pending: \(pendingFrames), inputPackets=\(bufferIn.packetCount), outputFrames=\(bufferOut.frameLength)")
}
outBuffers.append(bufferOut)
totalFrames += Int(bufferOut.frameLength)
}
return // wait for next handlePackets
case .endOfStream:
if verbose {
print("✅ convert returned endOfStream")
}
return
case .error:
if verbose {
print("❌ convert returned error")
}
if let error = error {
print("error converting: \(error.localizedDescription)")
}
return
@unknown default:
fatalError()
}
}
}
Hello,
I've discovered a buffer initialization bug in AVAudioUnitSampler that happens when loading presets with multiple zones referencing different regions in the same audio file (monolith/concatenated samples approach).
Almost all zones output silence (i.e. zeros) at the beginning of playback instead of starting with actual audio data.
The Problem
Setup:
Single audio file (monolith) containing multiple concatenated samples
Multiple zones in an .aupreset, each with different sample start and sample end values pointing to different regions of the same file
All zones load successfully without errors
Expected Behavior:
All zones should play their respective audio regions immediately from the first sample.
Actual Behavior:
Last zone in the zone list: Works perfectly - plays audio immediately
All other zones: Output [0, 0, 0, 0, ..., _audio_data] instead of [real_audio_data]
The number of zeros varies from event to event for each zone. It can be a couple of samples (<30) up to several buffers.
After the initial zeros, the correct audio plays normally, so there is no shift in audio playback, just missing samples at the beginning.
Minimal Reproduction
1. Create Test Monolith Audio File
Create a single Wav file with 3 concatenated 1-second samples (44.1kHz):
Sample 1: frames 0-44099 (constant amplitude 0.3)
Sample 2: frames 44100-88199 (constant amplitude 0.6)
Sample 3: frames 88200-132299 (constant amplitude 0.9)
2. Create Test Preset
Create an .aupreset with 3 zones all referencing the same file:
Pseudo code
<Zone array>
<zone 1> start : 0, end: 44099, note: 60, waveform: ref_to_monolith.wav;
<zone 2> start sample: 44100, note: 62, end sample: 88199, waveform: ref_to_monolith.wav;
<zone 3> start sample: 88200, note: 64, end sample: 132299, waveform: ref_to_monolith.wav;
</Zone array>
3. Load and Test
// Load preset into AVAudioUnitSampler
let sampler = AVAudioUnitSampler()
try sampler.loadAudioFiles(from: presetURL)
// Play each zone (MIDI notes C4=60, D4=62, E4=64)
sampler.startNote(60, withVelocity: 64, onChannel: 0) // Zone 1
sampler.startNote(62, withVelocity: 64, onChannel: 0) // Zone 2
sampler.startNote(64, withVelocity: 64, onChannel: 0) // Zone 3
4. Observed Result
Zone 1 (C4): [0, 0, 0, ..., 0.3, 0.3, 0.3] ❌ Zeros at beginning
Zone 2 (D4): [0, 0, 0, ..., 0.6, 0.6, 0.6] ❌ Zeros at beginning
Zone 3 (E4): [0.9, 0.9, 0.9, ...] ✅ Works correctly (last zone)
What I've Extensively Tested
What DOES Work
Separate files per zone:
Each zone references its own individual audio file
All zones play correctly without zeros
Problem: Not viable for iOS apps with 500+ sample libraries due to file handle limitations
What DOESN'T Work (All Tested)
1. Different Audio Formats:
CAF (Float32 PCM, Int16 PCM, both interleaved and non-interleaved)
M4A (AAC compressed)
WAV (uncompressed)
SF2 (SoundFont2)
Bug persists across all formats
2. CAF Region Chunks:
Created CAF files with embedded region chunks defining zone boundaries
Set zones with no sampleStart/sampleEnd in preset (nil values)
AVAudioUnitSampler completely ignores CAF region metadata
Bug persists
3. Unique Waveform IDs:
Gave each zone a unique waveform ID (268435456, 268435457, 268435458)
Each ID has its own file reference entry (all pointing to same physical file)
Hypothesized this might trigger separate buffer initialization
Bug persists - no improvement
4. Different Sample Rates:
Tested: 44.1kHz, 48kHz, 96kHz
Bug occurs at all sample rates
5. Mono vs Stereo:
Bug occurs with both mono and stereo files
Environment
macOS: Sonoma 14.x (tested across multiple minor versions)
iOS: Tested on iOS 17.x with same results
Xcode: 16.x
Frameworks: AVFoundation, AudioToolbox
Reproducibility: 100% reproducible with setup described above
Impact & Use Case
This bug severely impacts professional music applications that need:
Small file sizes: Monolith files allow sharing compressed audio data (AAC/M4A)
iOS file handle limits: Opening 400+ individual sample files is not viable on iOS
Performance: Single file loading is much faster than hundreds of individual files
Standard industry practice: Monolith/concatenated samples are used by EXS24, Kontakt, and most professional samplers
Current Impact:
Cannot use monolith files with AVAudioUnitSampler on iOS
Forced to choose between: unusable audio (zeros at start) OR hitting iOS file limits
No viable workaround exists
Root Cause Hypothesis
The bug appears to be in AVAudioUnitSampler's internal buffer initialization when:
Multiple zones share the same source audio file
Each zone specifies different sampleStart/sampleEnd offsets
Key observation: The last zone in the zone array always works correctly.
This is NOT related to:
File permissions or security-scoped resources (separate files work fine)
Audio codec issues (happens with uncompressed PCM too)
Preset parsing (preset loads correctly, all zones are valid)
Questions
Is this a known issue? I couldn't find any documentation, bug reports, or discussions about this.
Is there ANY workaround that allows monolith files to work with AVAudioUnitSampler?
Alternative APIs? Is there a different API or approach for iOS that properly supports monolith sample files?
Hi everyone!
I’ve developed a location-based Audio AR app in Unity with FMOD & Resonance Audio and AirPods Pro Head-Tracking to create a ubiquitous augmented soundscape experience. Think of it as an audio version of Pokémon Go, but with a more precise location requirement to ensure spatial audio is placed correctly.
I want this experience to run in the background on iOS, but from what I’ve gathered, it seems Unity doesn’t support this well. So, I’m considering developing a Swift version instead.
Since this is primarily for research purposes, privacy concerns are not a major issue in my case. However, I’ve come across some potential challenges:
Real-time precise location updates – Can iOS provide fully instantaneous, high-accuracy location updates in the background?
Continuous real-time data processing – Can an app continuously process spatial audio, head-tracking, and location data while running in the background?
I’m not sure if newer iOS versions have improved in these areas or if there are workarounds to achieve this.
Would this kind of experience be feasible to run in the background on iOS? Any insights or pointers would be greatly appreciated!
I’m very new to iOS development, so apologies if this is a basic question. Thanks in advance!
Hi there,
I recently launched a dj app to the mac app store, and was wondering how I could access songs for mixing purposes via Apple Music just like how serato, rekordbox, djay, and other DJ apps do?
Thanks,
Gunek
I have a Catalyst app ('container') which hosts an embedded AUv3 Audio Unit extension ('plugin'). This used to work for years and has worked with this project until a few days ago.
it still works on iOS as expected
on MacOS the extension is never registered/installed and won't load
extension won't show up with AUVal
seems to have stopped working with the 26.1 XCode update
I'm fairly certain the problem is not code related (i.e. likely build settings, project settings, entitlements, signing, etc.)
I have compared all settings with another still-working project and can't find any meaningful difference
(I can't request code-level support because even the minimal thing vastly exceeds the 250 lines of code limit.)
How can I debug the issue? I literally don't know where to start to fix this problem, short of rebuilding the entire thing and hope that it magically starts working again.
Hi!
I am writing a browser extension that allows you to control the playback of media content on a music service website. Unfortunately Safari does not support tracking changes to the audible property in an event tabs.onUpdated. Is there an alternative to this event? I'm looking for a way to track when the automatic inference engine interrupts playback on a music service website.
That you.
I'm using AVFoundation to make a multi-track editor app, which can insert multiple track and clip, including scale some clip to change the speed of the clip, (also I'm not sure whether AVFoundation the best choice for me) but after making the scale with scaleTimeRange API, there is some short noise sound in play back. Also, sometimes it's fine when play AVMutableCompostion using AVPlayer with AVPlayerItem, but after exporting with AVAssetReader, will catch some short noise sounds in result file.... Not sure why.
Here is the example project, which can build and run directly. https://github.com/luckysmg/daily_images/raw/refs/heads/main/TestDemo.zip
I am working on an app which plays audio - https://youtu.be/VbAfUk_eYl0?si=nJg5ayy2faWE78-g - and one of the features is, on restart, if you had paused playback of a file at the time the app was previously shut down (or were playing one at the time of shutdown), the paused state and position in the file is restored exactly as it was, on restart.
The functionality works. However, it seems impossible to get the "now playing" information in iOS into the right state to reflect that via the MediaPlayer API. On restart, handlers are attached to the play/pause/togglePlayPause actions on MPRemoteCommandCenter.shared(), and the map of media info is updated on MPNowPlayingInfoCenter.default().nowPlayingInfo.
What happens is that iOS's media view shows the audio as playing and offers a pause button - even though the play action is enabled and the pause action is disabled.
Once playback has been initiated (my workaround is to have the pause action toggle the play state, since otherwise you wouldn't be able to initiate playback from controls in a car without initiating it once from a device first).
I've created a simplified white-noise-player demo to illustrate the problem - simply build and deploy it, and then start the app, lock your device and look at the playback controls on the lock screen. It will show a pause button - same behavior I've described.
https://github.com/timboudreau/ios-play-pause-demo
I've tried a few things to narrow down the source of the issue - for example, thinking that not MPNowPlayingInfoPropertyPlaybackProgress and MPMediaItemPropertyPlaybackDuration might be the culprit (since the system interpolates elapsed time and it's recommended to update those properties infrequently) on startup might do the trick, but the result is the same, just without a duration or progress shown.
What governs this behavior, and is there some way to explicitly tell the media player API your current state is paused?